Method and apparatus to offload offgoing clutch torque with asynchronous oncoming clutch torque, engine and motor torque for a hybrid powertrain system

Abstract

A powertrain includes an electromechanical transmission mechanically-operatively coupled to an internal combustion engine and an electric machine adapted to selectively transmit mechanical power to an output member. A method for controlling the powertrain includes commanding a shift from a first operating range state to a second operating range state, identifying an off-going clutch, controlling torque output from said electric machine to offload reactive torque transmitted through said off-going clutch, selectively applying an oncoming clutch to offload reactive torque transmitted through said off-going clutch, and reducing a clutch torque capacity of said off-going clutch when said reactive torque transmitted through said off-going clutch is substantially zero.

1. Method for controlling a powertrain comprising an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and an electric machine adapted to selectively transmit mechanical power to an output member, said method comprising:
 commanding a shift from a first operating range state to a second operating range state; 
 identifying an off-going clutch; 
 controlling torque output from said electric machine to offload reactive torque transmitted through said off-going clutch; 
 selectively applying an oncoming clutch to offload reactive torque transmitted through said off-going clutch; and 
 reducing a clutch torque capacity of said off-going clutch when said reactive torque transmitted through said off-going clutch is substantially zero. 
 
     
     
       2. The method of  claim 1 , further comprising controlling torque output from a second electric machine to off-load reactive torque transmitted through said off-going clutch. 
     
     
       3. The method of  claim 1 , wherein selectively applying said oncoming clutch is based upon a torque required to assist said electric machine to fully offload reactive torque transmitted through said off-going clutch. 
     
     
       4. The method of  claim 3 , further comprising applying an engine torque based upon a torque required to assist said electric machine and said oncoming clutch to fully offload reactive torque transmitted through said off-going clutch. 
     
     
       5. The method of  claim 1 , wherein selectively applying said oncoming clutch is based upon determining that said oncoming clutch will reduce reactive torque in said off-going clutch. 
     
     
       6. The method of  claim 5 , wherein determining that said oncoming clutch will reduce reactive torque in said off-going clutch is based upon monitoring slip speed in said oncoming clutch. 
     
     
       7. The method of  claim 1 , wherein selectively applying said oncoming clutch is based upon determining a clutch energy limit and limiting said applying said oncoming clutch based upon said clutch energy limit. 
     
     
       8. Method for controlling a powertrain comprising an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and an electric machine adapted to selectively transmit mechanical power to an output member, said method comprising:
 initiating a shift event comprising
 identifying an off-going clutch to be synchronously offloaded, and 
 identifying an oncoming clutch to be loaded; 
 
 monitoring an electric machine torque capability to offload said off-going clutch; 
 determining a torque required to assist said electric machine to offload said off-going clutch; 
 applying torque with said electric machine to offload said off-going clutch; and 
 selectively applying torque through said oncoming clutch based upon said torque required to assist said electric machine to offload said off-going clutch. 
 
     
     
       9. The method of  claim 8 ,
 wherein monitoring an electric machine torque capability to offload said off-going clutch comprises
 monitoring a torque capability for said electric machine, and 
 monitoring a torque capability of a second electric machine; and 
 
 further comprising applying torque with said second electric machine to offload said off-going clutch. 
 
     
     
       10. The method of  claim 8 , further comprising:
 determining a torque required to assist said electric machine and said oncoming clutch to offload said off-going clutch; and 
 applying torque with said engine based upon said determining said torque required to assist said electric machine and said oncoming clutch to offload said off-going clutch. 
 
     
     
       11. The method of  claim 8 , further comprising:
 determining a clutch energy limit based upon intended operation of said oncoming clutch; and 
 wherein said selectively applying torque through said oncoming clutch is further based upon said clutch energy limit. 
 
     
     
       12. Apparatus for controlling a powertrain comprising an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and an electric machine adapted to selectively transmit mechanical power to an output member, said apparatus comprising:
 an identified off-going clutch; 
 an identified oncoming clutch; and 
 a powertrain control system including programming to
 monitor a torque capability of said electric machine to offload reactive torque from said off-going clutch, 
 determine a torque required to assist said electric machine to offload said off-going clutch, 
 command torque from said electric machine to offload said off-going clutch, and 
 selectively command torque through said oncoming clutch based upon said torque required to assist said electric machine to offload said off-going clutch. 
 
 
     
     
       13. The apparatus of  claim 12 , wherein said powertrain control system further includes programming to
 monitor a torque capability of a second electric machine to offload reactive torque from said off-going clutch, and 
 command torque from said second electric machine to offload said off-going clutch. 
 
     
     
       14. The apparatus of  claim 12 , wherein said powertrain control system further includes programming to
 determine a torque required to assist said electric machine and said oncoming clutch to offload said off-going clutch, and 
 command torque from said engine based upon said determining said torque required to assist said electric machine and said oncoming clutch to offload said off-going clutch. 
 
     
     
       15. The apparatus of  claim 12 , wherein said powertrain control system further includes programming to
 determine a clutch energy limit based upon intended operation of said oncoming clutch, and 
 limit said selectively commanded torque through said oncoming clutch based upon said clutch energy limit.